Initialize reference variables for many objects?

I'm having a little trouble building the grids for a Battleship game for my Java class. So far, I can easily make a for loop to add JPanel or JButton objects to the JFrame. However, my issue is that I'll need to use those Panels or Buttons again when playing the game (such as clicking on a button to see if your opponent put a ship on that square, et cetera). Is there a simple way in Java to initialize reference variables f开发者_Go百科or a LOT of objects? Or will I have to declare all of them individually?

You could try a multi dimensional array of JPanels (or any other object). Create an array with the same size as your grid. The line below initializes an array with 5 rows and 5 columns.

JPanel[][] battleField = new JPanel[5][5];

Use nested for loops to create the panels in the array.

for (int rowIndex = 0; rowIndex < battleField.length; rowIndex++)
{
    for (int cellIndex = 0; cellIndex < battleField[rowIndex]; cellIndex++)
    {
         battleField[rowIndex][cellIndex] = new JPanel();
    }
}

If you want to reference the battleField array later on you would just make it into a instance variable.

For a battleship game, you most likely want to retrieve the location of a button after is has been clicked. You can create a hashtable using your buttons as keys and the point it is located at as a value.

HashMap<JButton, Point> buttonMap = new HashMap<JButton, Point>();

for (int x = 0; x < COLUMNS; x++)
{
  for (int y = 0; y < ROWS; y++)
  {
     JButton btn = new JButton();
     btn.addActionListener(this);
     buttonMap.put(btn, new Point(x, y));
     //then add the button to your container
  }
}

The in your actionPerformed method you can convert the button to the point it is located at like this.

JButton btn = (JButton)actionEvent.getSource();
Point p = buttonMake.get(btn);

Of course you will need to properly handle error conditions such as source not being a button or the button not being in the map...

You can always extend JButton to keep track of the info you need. A simple example:

class MyButton extends JButton{
    private MyGameInfo mygameInfo;
    private int buttonId;
    //More fields....
    //Getters/Setters
}

Then instead of creating and adding JButton objects to your layout, create MyButton objects(which is also a JButton so your layout will not be effected) and use its extra functionality for your game logic.

For reference, here is a related matching game that uses a grid of buttons. This related answer demonstrates the application of the Model–View–Controller pattern to a simple game.